Rock drill



w; ALSMITH.

v nocx DRILL. APPLICATION man AUGJ3. 1920.

1,415,957, Patented May 16, 1922.

; NVENTOR TO NEY UNITED STATES PATENT OFFICE.

WILLIAM A. SMITH, P H ILLIPSBURG, NEW JERSEY, ASSIGINOR TO INGERSOLIrRAND COMPANY, OF JERSEY CITY, NEW JERSSEY, A CORPORATION 011 JERSEY.

To all whom it may concern: 3

Be it known that I, lViLLIAM A. SMITH, a citizen of the United States,and a resident of Phillipsburg, county of \Varren, State of New Jersey,have invented certain new and useful Improvements in Rock. Drills, ofwhich the following is a specification.

This invention relates to a fluid actuated rock drill of the hammertype, but more particularly to a machine of this type hav .ing a pistonhammer provided with two heads of equal diameter connected by a reducedneck, live fluid pressure being con stantly supplied to the cylinderbore at a point between the limits of travel. of said heads, anddistributed to the ends of the cylinder in front of and behind the saidheads, so that pressure is intermittently suppliedito and exhausted fromsaid cylinder ends.

A piston of the class described is ordinar- .ily a short stroke pistonand the primary objeets of the present invention are to produce a lateadmission against the rear surface of the rear head on the rearwardstroke, in order to give the piston a long back travel, and a latecut-ofi' on the forward stroke in order to give a long admission offluid pressure against the rear surface of the rear piston head. I amenabled to accomplish these objects by means of a valve controllingcommunication between forward and rearward admission passages leading totwo admission ports, one a forward port and the other located rearwardlyof said forward port. The distribution of fluid pressure is in all otherrespects controlledby the piston itself.

To these ends, the invention is shown .in one of its preferred forms inthe accompanying drawings, in which- Figures 1 and 2 are diagrammaticlongitudinal sectional elevations of arock drill embodying theinvention, showingthe piston hammer in two different positions.

Referring to the drawings, A represents the cylinder of a rock drillhaving the front head B through which the drill steel G extends inposition to receive the impact blows of the reciprocating piston hammer,which in this instance is formed with two heads D and E of equaldiameter connected by a reduced neck F. The piston may, if desired beprovided with the forwardly extending reduced shank Gr. The cylinder isprovided with a main bore H and. the back head J ROCK DRILL.

Specification of Letters Patent. Patented 11 16, 1922,

a Application filed August 13, 1920. Serial No. 403,353.

having the pressure chamber K. The cylinder A and back head J areprovided with Sllltitble ports and passages partly controlled by thepiston and partly controlled by a valve L for distributing fluidpressure to different portions of the cylinder for actuating the piston.

Actuating fluid as air under pressure is constantly supplied to thecylinder bore from the inlet 0 at a point between the limits of travelof the said two heads D and r E, and the admission port P is openconstantly for this purpose. Pressure is intermittently supplied to therear pressure chamber K in the back head and to the forward end of thecylinder in front of the piston head I). The back head is provided withthe exhaust port Q, and the main cylinder bore is provided with theexhaust port R. Admission of fluid pressure to the forward end of themain cylinder bore is controlled solely by the front piston head throughthe supply port S, passage T and admission port U directly to the frontend. of the cylinder.

A forward admission port V comment cates with the valve chamber W bymeans of the forward admission passage X, and another rearward admissionport Y communicates with the valve chamber W by means of the rearwardadmission passage Z. The rearward admission passage Z comu'iuuicatcswith the rear pressure chamber K in the back head J by means of thepassage (1.. The valve I) is provii'led with the forward. and rearwardheads 2) and (3: connected by the reduced neck (Z. Opposed. operativepressure surfaces of the valve are subject to fluctuating pressure andin this instancethe forward surface 0 is intermittently supplied withpressure through the passage. f communicating with the supply port Swhile the rear pressure surface of the valve is intermittently suppliedwith pressure through the passage it communicating with thesupplypassage to. The function of the valve is to control communica tionbetween the forward admission passage X and the rearward admissionpassage Z in order to produce a late admission of fluid pressure againstthe rear pressure surface 7' of the rear piston head E on the rearwardstroke and prolong the admission. The piston thus has a longer backtravel than customary in rock drills having a piston of this type, andhas a later out-off on the forward stroke.

In the operation of the machine, let it be assumed that the piston is attheforward end of its stroke and is about to start on the back stroke asindicated in Figure 1. The rear pressure chamber K in the back head isshown exhausting through the exhaust port Q and pressure is alsoexhausted from the rear end of the valve L through the passages h, a,and through the chamber K and exhaust port Q. The live pressure on thefront surface 6 of the valve L has caused the valve to be thrown to itsrearward position as indicated in Figure 1, closing communicationbetween the forward and rearward admission passages X and Z.

In Figure 1, the fluid pressure is being admitted to the front end ofthe main cylinder bore in front of the piston head D, and as the pistontravels back the exhaust port Q for the rear pressure chamber K in theback end is closed and the supply port S to the forward end of thecylinder is closed, but the shoulder 70 at the neck of the pistonover-runs the forward admission port V without admitting pressure to therear surface j of the piston head E, because the forward admissionpassage X is still closed by the valve L.

After the forward piston head D overruns the cylinder exhaust port R,the exhaust from the forward end of the cylinder is opened, which alsoopens the front end a of the valve L to exhaust through the passages fand T and through the cylinder bore to the exhaust port'R; The shoulder70 on the neck of the piston-then over-runs the rearward admission portY as indicated in Figure 2, which admits pressure past the piston neckFto the rear pressure chamber K behind the piston head E and also admitspressure through the assage ii to the front end 9 of the valve L w iichthrows the Valve to its rear position, also as indicated in Figure 2,thus opening communication between the forward alnd rearward admissionpassages X and Z and supplies full pressure behind the piston head E todrive the piston forward.

Owing to the fact that no pressure is supplied to the rear of the pistonhead E when the forward admission port V is uncovered by the pistonshoulder is, the piston has a substantiallylong rearward stroke, beforethe forward and rearward admission passages X and Z are placed incommunication by the action of the valve L, and on the other hand, thepiston is given a late cut-01f on the forward stroke, because cut-oildoes not take place when the rearward admission port Y is over-run bythe piston shoulder in, but is delayed until the forward admission portV is over-run by the piston as indicated in Figure l.

I claim:

1. In a fluid operated rock drill of the hammer type, the combination ofa cylinder and piston having front and rear heads of equal diameter, anda connecting neck of reduced diameter, means for constantly supplyingfiuid under pressure to the cylinder between the said two piston heads,a supply port controlled solely by the front piston head andcommunicating by means of a supply passage with an admission port at thefront end of the cylinder for supplying motive fluid directly to theforward end of the cylinder in front of the front piston head, a forwardadmission port and another admission port rearward of the said forwardadmission port for supplying motive fluid to the rearward end of thecylinder behind the rear piston head, and a fluid actuated valve forcontrolling communication between forward and rearward admissionpassages leading to said forward and rearward admission ports.

2. In a fluid operated rock drill of the hammer type, the combination ofa cylinder and piston having front and rear heads of equal diameter, anda connecting neck of reduced diameter, means for constantly supplyingfluid under pressure to the cylinder between the said two piston heads,a supply port controlled solely by the front piston head andcommunicating by means of a supply passage with an admission port at thefront end of the cylinder for supplying motive fluid directly to theforward end of the cylinder in front of the front piston head. a forwardadmission port and another admission port rearward of the said. forwanladmission port for supplying motive Iluid to the rearward end of thecylinder behind the rear piston head, and a fluid actuated valve subjectto fluctuating pressure on opposed operative surfaces, for controllingcommunication between forward and rearward admission passages leading tosaid forward and rearward admission ports.

In testimony whereof I have signed this specification.

WILLIAM A. SMITH.

